Measurements of atomic hydrogen recombination coefficients and the reduction of Al2O3 using a heat flux sensor

The knowledge of atomic hydrogen recombination coefficient (γ) is essential for plasma simulations to calculate accurate atomic hydrogen fluxes. However, γ is a complex material property, and it is affected by the experimental conditions under which it is measured. Therefore, values of γ can differ even by a few orders of magnitude for the same material. In this paper, we demonstrate measurements of hydrogen recombination coefficients at room temperature using an in-house-built catalytic sensor for two selected materials: aluminum Al-5083 (alimex) and stainless steel 316 l, under the load of low-temperature H2 plasma with an admixture of H2O or N2 gases. The plasma settings were carefully chosen to mimic properties of the so-called extreme ultraviolet-generated plasma.1 The measured γ values agree well with literature data obtained for similar plasma conditions and show a correlation with ion energy. Additionally, we show a novel application of the sensor for indirect measurements of the reduction of oxidized surfaces as a function of ion dose. In these experiments, a correlation between reduction time and background water pressure is observed.